Controls (continued)
operation, the pressure within the building in monitored by the OptiLogic™ controller. If the pressure rises to or above a selected
Powered Variable Volume Exhaust-Discharge Damper Controlled
This optional variable volume powered exhaust system consists of a fixed speed fan configured with a propor- tionally controlled discharge damper. The OptiLogic™ controller monitors the pressure inside the building and controls the Exhaust Damper and the Exhaust Fan. If the Building Pressure rises, the Exhaust Damper is pro- portionally controlled open and the Exhaust Fan is con- trolled ON. If the Building Pressure falls, the Exhaust Damper is proportionally controlled closed and the Ex- haust Fan is controlled OFF. The position of the Ex- haust Damper in which the Exhaust Fan is controlled ON and OFF as well as the Building Pressure setpoint is user selectable from the OptiLogic™ User Interface.
Powered Variable Volume Exhaust-VFD Controlled
This optional variable volume powered exhaust system consist of an Exhaust Fan driven by a Variable Fre- quency Drive (VFD), which is controlled by the OptiLogic™ controller. The OptiLogic™ controller moni- tors the pressure within the building. As the pressure rises, the VFD is controlled to increase Exhaust Fan speed. As the pressure falls, the VFD is controlled to decrease Exhaust Fan speed. The Building Pressure Setpoint is user selectable from the OptiLogic™ User Interface.
LOW AMBIENT OPERATION
The OptiLogic™ controller continuously monitors the outside air temperature to determine if mechanical cool- ing should be allowed. As a safety, if the Outside Air temperature falls to or below the Low Ambient Lockout temperature, mechanical cooling is prevented from op- erating. For units with economizers, the Low Ambient Lockout temperature is typically low enough that me- chanical cooling will rarely be required. However, for some applications mechanical cooling is required when the Outside Air temperature is lower than the Low Am- bient Lockout temperature.
For these applications, the unit can be equipped with optional Low Ambient controls. For optional Low Ambi- ent operation, the OptiLogic™ controller monitors the refrigeration system discharge pressure and controls the speed of the condenser fans. If the discharge pres- sure falls, the speeds of the condenser fans are re- duced to maintain acceptable condensing pressures in the refrigeration system. With the optional Low Ambi- ent controls, mechanical cooling is allowed down to Outside Air temperatures of 0°F.
SMOKE PURGE SEQUENCES
General
As a convenience, for when buildings catch fire or the building is inundated with smoke or fumes from manu- facturing processes, etc., the OptiLogic™ control sys- tem provides one of five ventilation override control se- quences for building purge. The five selectable purge sequences are, Shutdown, Pressurization, Exhaust, Purge and Purge with duct pressure control. Note, when any of the purge sequences are activated, cooling and heating modes are disabled. A contact closure is pro- vided which indexes the OptiLogic™ controller into the selected purge sequence.
Shutdown
When this purge sequence is selected and activated, the supply and exhaust fans are controlled OFF and the Outside Air damper is overridden closed. This idle state is maintained until the purge input is deactivated and the unit returns to normal operation.
Pressurization
When this purge sequence is selected and activated, the exhaust fan is controlled OFF and the Supply Fan is controlled ON. The Outside Air damper is opened full and the Return Air Damper is closed full. If the unit is a VAV unit, the VAV boxes are also driven full open to prevent duct
Exhaust
When this purge sequence is selected and activated, the Supply Fan is controlled OFF and the Exhaust Fan is controlled ON (Exhaust Damper driven full open). This mode is maintained until the smoke purge input is deactivated and the unit returns to normal operation.
28 | YORK INTERNATIONAL |